The present invention relates to fluid brake systems for vehicles. More particularly, the invention involves the integration of anti-lock braking control into a vehicle's fluid brake system.
The subject of this application is related to the following co-pending patent applications: U.S. Ser. No. 08/363,080 entitled "Hydraulic ABS Modulator" and U.S. Ser. No. 08/362,229, now U.S. Pat. No. 5,538,336, entitled "Integrated ABS/TCS Hydraulic Modulator Braking System," both commonly assigned, filed concurrently with this specification and both of which are hereby, specifically incorporated herein by reference.
Conventional vehicle fluid brake systems are characterized by providing the ability for effective wheel braking in response to manual application of force to a brake pedal actuator. The art has adapted the conventional vehicle fluid brake system to automatic control mechanisms which intervene in the event of certain conditions and provide advanced braking functions. One such mechanism, an anti-lock braking system (ABS), generally represents a combination of hydraulic and electric control.
A typical ABS system inhibits the vehicle's wheel brakes from locking up by releasing the applied fluid pressure when an incipient wheel lockup condition is sensed. After release of the fluid pressure wheel deceleration ceases and the wheel begins accelerating toward vehicle speed. When the wheel speed has substantially recovered braking fluid pressure is reapplied. Reapplication of fluid pressure generally results in the wheel again approaching lockup and the cycle is repeated.
The art has proposed that ABS functions can be provided by employing several different mechanisms. The problem posed in developing an ABS braking system is to provide optimum operation considering system response, adaptability and efficiency while concurrently avoiding unnecessary complexity and cost. This presents a significant challenge in the development of vehicle braking systems.